This invention relates to a hydraulic damper and, particularly to a hydraulic damper of the adjustable damping force type.
One prior art hydraulic damper of the adjustable damping force type comprises a cylinder containing hydraulic fluid therein, a piston working in the cylinder and partitioning the interior thereof into two liquid chambers, a piston rod connected to the piston and extending through one of the liquid chambers to project to the outside of the cylinder, a liquid passage formed in the piston rod for communicating said two liquid chambers, and an adjusting member for adjusting the effective passage area of the liquid passage. The adjusting member is rotatably disposed in the piston rod to selectively open or close a plurality of radial openings which are provided in the piston rod to constitute a part of the liquid passage. Usually, a sensor is provided to detect the angular position of the adjusting member to generate an electric signal to actuate an indicator which is preferably mounted in an instrument panel of an automobile so that the driver of the automobile can easily observe the adjusted condition of hydraulic dampers.
When a digital encoder is utilized to detect the adjusted positions of the adjusting member, there is a problem that when a digital signal representing an adjusted position of the adjusting member has the same digit (1 or 0) at different columns, it is required that the detection should be performed simultaneously, an otherwise a false signal may be transmitted to an electric circuit connected to the digital encoder and the adjusting member may not sometimes be set to the desired adjusted position.